Q&A - PSLE Science

[the kiasu student]

One of the questions from today’s paper was like this:


A 200cm metal rod was heated for 20mins and expanded to a length of 210cm. John took another 200cm metal rod, made of the same type of metal, but thicker. He heated it for 20mins. Will the length of the thicker rod be shorter or longer than 210cm or be the same? Explain.

My answer: Longer. The amount of matter in the thicker rod was more than the amount of matter in the first rod, hence the thicker rod would expand to more than 210cm.

[triplediao]

the kiasu student:

One of the questions from today's paper was like this:


A 200cm metal rod was heated for 20mins and expanded to a length of 210cm. John took another 200cm metal rod, made of the same type of metal, but thicker. He heated it for 20mins. Will the length of the thicker rod be shorter or longer than 210cm or be the same? Explain.

My answer: Longer. The amount of matter in the thicker rod was more than the amount of matter in the first rod, hence the thicker rod would expand to more than 210cm.

On the other hand, my ans:

The length would be shorter than 210mm. The volume of the rod would be greater than that of the rod intially used. Since the greater the volume, the longer it takes for the temperature of the rod to increase, during the 20min, the rod initially used would gain more heat allowing it to expand more.

[youngtay]

Muffins


Thanks.

[MOE Hater]

triplediao:

the kiasu student:

One of the questions from today's paper was like this:


A 200cm metal rod was heated for 20mins and expanded to a length of 210cm. John took another 200cm metal rod, made of the same type of metal, but thicker. He heated it for 20mins. Will the length of the thicker rod be shorter or longer than 210cm or be the same? Explain.

My answer: Longer. The amount of matter in the thicker rod was more than the amount of matter in the first rod, hence the thicker rod would expand to more than 210cm.

On the other hand, my ans:

The length would be shorter than 210mm. The volume of the rod would be greater than that of the rod intially used. Since the greater the volume, the longer it takes for the temperature of the rod to increase, during the 20min, the rod initially used would gain more heat allowing it to expand more.

My teacher said that if they ask why A is shorter than B for instance, u should only answer why A is shorter than B, not why B is longer than A. Ur ans is the latter not the former, so if they are strict, u may be penalised.

Not to rain on ur post-PSLE parade or anything, but juz sharing...

[Muffins]

youngtay:

Muffins


Thanks.

you're very welcome!

[meimeitan]

Hi All,


May I know :

there are three sets of electric curcuits set as follows:

(1) two batteries arranged in series with one bulb
(2) two batteries arranged in parallel with one bulb
(3) three batteries arranged in parallel with one bulb

are the brightness of the bulb the same?

thanks

meimeitan

[starlight1968sg]

meimeitan:

there are three sets of electric curcuits set as follows:


(1) two batteries arranged in series with one bulb
(2) two batteries arranged in parallel with one bulb
(3) three batteries arranged in parallel with one bulb

are the brightness of the bulb the same?
meimeitan

No.
The bulb in (1) will be the brightest among the set-ups.
The bulbs in (2) and (3) will have the same brightness. :roll:

[meimeitan]

Hi!


Thanks.

meimeitan

[meimeitan]

Hi All,


I have come across the following questions. May I know the possible answer?

Mr Goh concluded that the increase in his height from birth until he was 21 years old was due to cell division. What other factor contributed to this increase in height?

Is the answer ‘cell growth’?

Thanks.

meimeitan

[atutor2001]

meimeitan:

Hi All,


I have come across the following questions. May I know the possible answer?

Mr Goh concluded that the increase in his height from birth until he was 21 years old was due to cell division. What other factor contributed to this increase in height?

Is the answer 'cell growth'?

Thanks.

meimeitan

You are correct. Just some additional points you may wish to know :

There are 2 purposes/functions for/of cell division :
1. To replace old or damaged cells
2. For growth (i.e. increase the number of cells)

There are 2 definitions for cell growth :
1. Increase in number of cells - this is the reason for an organism growing bigger. (When an organism reaches matured stage, cell growth will slow down and finally stop. Then cell division is only for replacement purposes.)
2. The cell itself growing bigger - this is the process of a cell development

Many kids find above confusing.